Science · Primary 6 · The Web of Life · Semester 1

Competition and Predation

Examine the dynamics of inter- and intra-species competition and predator-prey relationships.

• MOE Syllabus Outcomes
• MOE: Interactions within the Environment - S1

About This Topic

Competition and predation shape population sizes and ecosystem balance. Intraspecific competition pits individuals of the same species against each other for resources such as food, water, or territory, often limiting population growth. Interspecific competition arises between different species, where the better-adapted one may dominate. Predator-prey relationships feature predators controlling prey numbers through hunting, while prey populations rebound when predators are scarce, creating cycles observable in data like lynx and hare populations.

This topic anchors the Web of Life unit by linking interactions to environmental stability. Students compare competition effects on populations and analyze how predation prevents overpopulation. They also predict disruptions, such as prey explosions followed by resource crashes if a key predator vanishes, building skills in pattern recognition and causal reasoning essential for science.

Active learning suits this topic perfectly. Simulations where students act as predators collecting prey tokens or compete in resource-limited games reveal dynamic shifts in real time. These experiences turn abstract models into visible patterns, deepen understanding of balance, and spark discussions on local examples like otters and fish in Singapore mangroves.

Key Questions

1. Compare the effects of interspecific and intraspecific competition on populations.
2. Analyze how predator-prey relationships regulate population sizes.
3. Predict the long-term consequences for an ecosystem if a key predator is removed.

Learning Objectives

• Compare the impact of intraspecific and interspecific competition on the population growth rates of two hypothetical species.
• Analyze data to explain how predator-prey cycles, such as those between rabbits and foxes, influence population sizes over time.
• Predict the cascading effects on an ecosystem, including resource depletion and population crashes, if a keystone predator like the Malayan tiger were removed from Singapore's nature reserves.
• Explain the mechanisms by which competition for limited resources, like food and territory, affects individual survival and reproduction within a species.

Before You Start

Food Chains and Food Webs

Why: Students need to understand the flow of energy and the roles of producers, consumers, and decomposers to grasp how competition and predation fit into the larger ecosystem structure.

Basic Population Concepts

Why: Understanding what a population is and how it can change in size is fundamental to analyzing the effects of competition and predation on population dynamics.

Key Vocabulary

Intraspecific Competition	Competition for resources that occurs between individuals of the same species, such as two squirrels fighting over the same nut.
Interspecific Competition	Competition for resources that occurs between individuals of different species, like different types of fish competing for algae in a pond.
Predator	An organism that hunts and kills other organisms for food, for example, a snake eating a mouse.
Prey	An organism that is hunted and killed by another organism for food, such as a fish being eaten by a kingfisher.
Population Regulation	The process by which factors like predation and competition control the size of a population, preventing it from growing indefinitely.

Watch Out for These Misconceptions

Common Misconception

Predators always wipe out prey populations.

What to Teach Instead

Populations cycle as prey rebounds when predators starve. Simulations with tokens show oscillations, helping students visualize lags and recoveries through group graphing and discussion.

Common Misconception

Competition only involves fighting for food.

What to Teach Instead

It includes space, mates, and light too. Relay games with varied resources expose multiple factors, prompting students to revise ideas via peer comparison of outcomes.

Common Misconception

Removing a predator benefits the ecosystem.

What to Teach Instead

It causes prey booms, resource depletion, and crashes. Role-plays demonstrate disruptions, guiding students to connect actions to long-term stability through shared predictions.

Active Learning Ideas

Simulation Game: Predator-Prey Cycles

Scatter 100 beans as prey on the floor. Pairs act as predators collecting 10 beans per round in 1 minute, then add prey based on survivors. Graph population changes over 10 rounds. Discuss cycles and regulation.

45 min·Pairs

Relay: Resource Competition

Set limited resource cards (food, space) at stations. Small groups relay to claim cards, competing intraspecifically within groups or interspecifically between groups. Tally survivors and note effects on 'population' sizes. Reflect on winners and losers.

35 min·Small Groups

Data Analysis: Lynx-Hare Graphs

Provide historical population data tables. In small groups, students plot line graphs for predator and prey over decades. Identify peaks, lags, and crashes, then predict outcomes without predators.

40 min·Small Groups

Role-Play: Ecosystem Disruption

Assign roles in a food web: prey, predators, plants. Whole class acts out normal balance, then removes a predator. Observe chain reactions like prey overgrowth and plant depletion. Debrief predictions.

50 min·Whole Class

Real-World Connections

• Wildlife biologists studying the Sungei Buloh Wetland Reserve observe competition between resident and migratory bird species for food sources, informing conservation strategies.
• Farmers managing fruit orchards in Cameron Highlands, Malaysia, must control populations of pests like fruit flies through natural predators or competition management to protect crops.
• Marine scientists monitor coral reef ecosystems, noting how different fish species compete for space and food, and how the removal of a predator like a shark can lead to an overabundance of herbivorous fish that damage the coral.

Assessment Ideas

Quick Check

Present students with two scenarios: 1) A group of deer competing for limited grass. 2) Eagles and hawks competing for the same rodent prey. Ask students to identify the type of competition in each scenario and explain one potential outcome for the populations involved.

Discussion Prompt

Pose the question: 'Imagine the monitor lizards, a key predator in some Singaporean ecosystems, were suddenly removed. What are two specific changes you would expect to see in the populations of other animals and plants in that area, and why?' Facilitate a class discussion to explore cause and effect.

Exit Ticket

On an index card, students will draw a simple diagram showing either an intraspecific or interspecific competition scenario. Below the diagram, they will write one sentence explaining the interaction and one sentence predicting a consequence for one of the organisms.

Frequently Asked Questions

What are examples of intraspecific competition in Singapore ecosystems?

In Bukit Timah Nature Reserve, monkeys compete for fruit trees within troops, limiting group size. Seedlings vie for sunlight under dense canopies. Students can map local parks to spot overcrowding signs like stunted growth, connecting observations to population limits.

How does predation regulate prey populations?

Predators keep prey from exceeding resource capacity, preventing starvation crashes. Cycles show prey peaks followed by predator increases, then prey drops. Graphing real data like otters and crabs in mangroves helps students see this balance in action.

How can active learning help teach competition and predation?

Games and simulations let students embody roles, witnessing population swings firsthand. For instance, bean hunts as predator-prey reveal cycles that lectures miss. Group reflections build causal links, making abstract dynamics tangible and relevant to Singapore habitats.

What happens if a key predator is removed from an ecosystem?

Prey populations surge, overconsuming resources and causing declines in plants or smaller prey. This triggers secondary crashes. Role-plays or models predict outcomes like those from cane toad introductions, emphasizing predator roles in stability.